Java Day 19

 1 package com.company.Day019;
 2 
 3 import java.util.HashMap;
 4 import java.util.Iterator;
 5 import java.util.LinkedHashMap;
 6 import java.util.Map;
 7 
 8 /**
 9  * Created by junius on 2016/10/15.
10  */
11 public class HashMap001 {
12     public static void main(String[] args){
13         HashMap<Integer,String> hm = new LinkedHashMap<Integer,String>();
14         hm.put(7,"zhouqi");
15         hm.put(5,"zhouqi3");
16         hm.put(2,"zhouqi2");
17 
18         Iterator<Map.Entry<Integer,String>> it = hm.entrySet().iterator();
19 
20         while(it.hasNext()){
21             Map.Entry<Integer,String> me = it.next();
22             Integer key = me.getKey();
23             String value = me.getValue();
24 
25             System.out.println(key+" : "+value);
26         }
27     }
28 }

 1 package com.company.Day019;
 2 
 3 import java.util.Iterator;
 4 import java.util.Map;
 5 import java.util.TreeMap;
 6 
 7 /**
 8  * Created by junius on 2016/10/10.
 9  * "fagavcbascdfs" 字母次数  映射关系
10  * 1、字符串变成字符数组
11  * 2、遍历字符数组，用每一个字母做键 查map表
12  * 如果字母键不存在，就值为1
13  * 存在,则值+1
14  * 3、遍历
15  */
16 public class MainDemo002 {
17     public static void main(String[] args){
18         String str = "abcefgabcabcooi";
19         String s = getCharCount(str);
20         System.out.println(s);
21     }
22 
23     public static String getCharCount(String str) {
24         //字符串转换成字符数组
25         char[] chs = str.toCharArray();
26 
27         //定义map集合
28         Map<Character,Integer> map = new TreeMap<Character,Integer>();
29 
30         for (int i = 0; i <chs.length ; i++) {
31             /*if(value==null)
32                 map.put(chs[i],1);
33             else{
34                 map.put(chs[i],value+1);
35             }*/
36             if(!(chs[i] >= ‘a‘ && chs[i] <= ‘z‘ || chs[i] >= ‘A‘ &&chs[i] <= ‘Z‘))
37                 continue;
38             int count = 0;
39             Integer value = map.get(chs[i]);
40 
41             if(value != null){
42                 count = value;
43             }
44             count++;
45             map.put(chs[i],count);
46         }
47 
48         return mapToString(map);
49     }
50 
51     private static String mapToString(Map<Character, Integer> map) {
52         StringBuilder sb = new StringBuilder();
53         Iterator<Character> it = map.keySet().iterator();
54         while(it.hasNext()){
55             Character key = it.next();
56             Integer value = map.get(key);
57             sb.append(key+"("+value+")");
58         }
59         return sb.toString();
60     }
61 
62 }

 1 package com.company.Day019;
 2 
 3 import java.util.*;
 4 
 5 public class MapTest003 {
 6     public static void main(String[] args){
 7 
 8         demo_2();
 9     }
10 
11     private static void demo_2() {
12         List<String> list = new ArrayList<String>();
13         list.add("zzzA");
14         list.add("yyyYY");
15         list.add("dd");
16         list.add("aaa");
17         System.out.println(list);
18 //        Collections.sort(list);
19 //        mySort_2(list,new comparatorByLength());
20         Collections.sort(list,new comparatorByLength());
21         System.out.println(list);
22 
23     }
24 
25     private static void demo_1() {
26 
27         List<String> list = new ArrayList<String>();
28         list.add("zzz");
29         list.add("yyy");
30         list.add("ddd");
31         list.add("aaa");
32         System.out.println(list);
33 //        Collections.sort(list);
34         mySort(list);
35         System.out.println(list);
36 
37     }
38 
39     public static <T extends Comparable<? super T>> void mySort(List<T> list){
40         for (int i = 0; i <list.size()-1 ; i++) {
41             for (int j = i+1; j <list.size(); j++) {
42                 if(list.get(i).compareTo(list.get(j))>0){
43 //                    String temp = (String)list.get(i);
44 //                    list.set(i,list.get(j));
45 //                    list.set(j,(T)temp);
46                     Collections.swap(list,i,j);
47                 }
48             }
49         }
50     }
51 
52     public static <T> void mySort_2(List<T> list,Comparator<? super T> comp){
53         for (int i = 0; i <list.size()-1 ; i++) {
54             for (int j = i+1; j <list.size(); j++) {
55                     if(comp.compare(list.get(i),list.get(j))>0) {
56                         Collections.swap(list, i, j);
57                     }
58                 }
59             }
60     }
61 }

 1 package com.company.Day019;
 2 
 3 import java.util.ArrayList;
 4 import java.util.List;
 5 
 6 /**
 7  * Created by junius on 2016/10/15.
 8  */
 9 public class Lock004 {
10     public static void main(String[] args){
11         List list = new ArrayList();//非同步
12         list = MyCollections.synList(list);//同步list
13     }
14 }
15 class MyCollections{
16     public static List synList(List list){
17         return new Mylist(list);
18     }
19 
20     private class Mylist implements List{
21         @Override
22         public List subList(int fromIndex, int toIndex) {
23             return null;
24         }
25 
26         private List list;
27         private final Object lock = new Object();
28 
29         public MyList(List list){
30             this.list = list;
31         }
32 
33         public boolean add(Object obj){
34             synchronized(lock){
35                 return list.add(obj);
36             }
37 
38         }
39 
40         public boolean remove(Object obj){
41             synchronized(lock) {
42                 return list.remove(obj);
43             }
44         }
45 
46     }
47 }

 1 package com.company.Day019;
 2 
 3 import java.util.Arrays;
 4 import java.util.List;
 5 
 6 /**
 7  * Created by junius on 2016/10/15.
 8  */
 9 public class Arrays005 {
10     public static void main(String[] args){
11 
12         demo_2();
13 //        System.out.println(myToString(arr));
14         String[] str = {"abc","abb","abd"};
15 
16         //将数组转换成集合
17 //      好处：可以使用集合的方法
18 //      弊端：对于集合的增删方法不可用
19         List<String> list = Arrays.asList(str);
20         boolean b = list.contains("abc");
21         System.out.println("list b = "+b);
22     }
23 
24     private static void demo_2() {
25         int[] arr = {2,3,4,5,7};
26         List<int[]> list = Arrays.asList(arr);
27         System.out.println(list);
28     }
29 
30     private static String myToString(int[] a){
31         if (a == null)
32             return "null";
33         int iMax = a.length - 1;
34         if (iMax == -1)
35             return "[]";
36 
37         StringBuilder b = new StringBuilder();
38         b.append(‘[‘);
39         for (int i = 0; ; i++) {
40             b.append(a[i]);
41             if (i == iMax)
42                 return b.append(‘]‘).toString();
43             b.append(", ");
44         }
45     }
46 
47 
48 }

 1 package com.company.Day019;
 2 
 3 import java.util.*;
 4 
 5 /**
 6  * Created by junius on 2016/10/15.
 7  * Collection 的 toArray方法
 8  *
 9  */
10 public class toArray006 {
11     public static void main(String[] args){
12         List<String> list = new ArrayList<String>();
13         list.add("abc1");
14         list.add("abc4");
15         list.add("abc3");
16         String[] str = list.toArray(new String[list.size()]);
17         //toArray方法需要传入 一个指定类型的数组
18         //如果长度小于集合的size,该方法会创建一个同类型并和集合相同size的数组
19         //如果长度大于集合的size,则数组中其他多余的位置存储null
20         //所以建议长度指定为集合的size.
21         //System.out.println(Arrays.toString(str));
22 
23         /*foreach语句
24          *for(类型 变量 ： Collection集合|数组)
25          * 只用于遍历，不会对元素进行过多的操作
26          *
27          * 与普通for的区别
28          * 1、普通for可以定义控制循环的增量和条件
29          *    增强for是简化形式，必须要有遍历的目标
30          */
31         for (String str2 : str) {
32             System.out.println(str2);
33 
34         }
35 
36         Map<Integer,String> map = new HashMap<Integer,String>();
37         map.put(3,"lisi1");
38         map.put(4,"lisi2");
39         map.put(2,"lisi3");
40         map.put(5,"lisi4");
41 
42         for(Integer key:map.keySet()){
43             String value = map.get(key);
44             System.out.println(key+" : "+value);
45         }
46 
47         for(Map.Entry<Integer,String> me:map.entrySet()){
48             Integer key = me.getKey();
49             String value = me.getValue();
50             System.out.println(key+" : "+value);
51         }
52 
53         int sum = add(4,6);
54 
55          System.out.print(newAdd(2,1,2,3,4,5,6));
56 
57     }
58 
59     public static int add(int a,int b){
60         return a+b;
61     }
62 
63     /*
64     * 注意事项 可变参数类型，必须定义在参数列表的结尾
65     */
66     public  static int newAdd(int... arr){
67         int sum = 0;
68         for (int i = 0; i <arr.length ; i++) {
69             sum += arr[i];
70         }
71         return sum;
72     }
73 
74 
75 }